Mac OS X Lion merges some aspects of iOS with the Mac environment, like the new Launchpad feature for launching apps.

OSX Lion has already begun to blur the lines between Mac and iOS. But in a note to investors today first reported by Barron’s, a Jefferies & Co. analyst believes the two will completely merge by 2012.

How will this be accomplished? On the hardware end, analyst Peter Misek posits that Apple could use the A6 quad-core processor to unify its mobile and computing devices.

“We believe Apple is ready to start sampling the A6 quad-core app processor and will be the first to such multi-device platform capable of PC-like strength,” Misek says.

We’ve already said that it’s possible that Apple plans to eventually eliminate its professionally-targeted device lines, especially since size is such a determining factor in consumer purchases now. Having one unified experience across devices, especially when they’re so similar in size (11-inch MacBook Air? 10-inch iPad? Completely different user experiences?), would certainly make sense and simplify consumers’ computing. OSX Lion, which debuted recently, married some aspects of iOS with Mac OSX, but a little less successfully than many had hoped. And more widespread cloud-based storage like iCloud will keep things smooth and consistent no matter what device you’re using.

One of the key points Misek’s note makes in Apple’s merging of the two distinct operating systems (well, slightly less distinct now with OSX Lion) is that Apple hopes to provide a seamless experience for its users across multiple devices.

“Users want to be able to pick up any iPhone, iPad, or Mac (or turn on their iTV) and have content move seamlessly between them and be optimized for the user and the device currently being used,” he says in the note. If OS X and iOS are separate entities, that’s more difficult to accomplish.

And by using a single processor type across handheld devices like the iPhone, as well as larger ones like the MacBook Air, implementing that single, unified OS becomes much more straightforward than needing to adapt it to different chipsets. Of course, higher-end products like the iMac or MacBook pro may require a little bit longer to completely merge into this ARM-based ecosystem.

“Apple can use a 32-bit ARM architecture to address the vast majority of the OS X ecosystem’s needs in 2012-13 except for high-end professional devices,” Misek wrote in his note. “When 64-bit ARM is available in 2016, we believe Apple will have a single OS and hardware architecture.” Rumors about Apple switching to using ARM architecture in both its MacBook Airs and Macs have persisted for a while now.

In addition to making sense for users, unifying OSX and iOS would also benefit Apple. iAd would have a significantly larger audience. App developers would potentially have less differentiation to deal with between products, especially now that HTML 5 is really taking off. Misek believes lower research and development costs would be required as well, as innovation would be performed on a single OS instead of paralleled across multiple ones, and content licensing would become a more streamlined process.